To add to what Ben
said, stone pickaxes can also mine coal.
Also keep in mind that gold is not very useful for making any tools (shovels, pickaxes, axes, hoes, swords). While you can do it, they're relatively low-durability items and not worth wasting the comparatively rare gold on.
Sand obeys gravity but sandstone
does not. It can be hard to tell the difference sometimes, until you get up close.
Definitely make use of the Minecraft Wiki to learn all about the game mechanics! It is always being updated as the game is enhanced so I use it to find out about new blocks and whatnot as they are made available.